The goals of the projects are to evaluate molecular mimicry as a mechanism of pathogenesis for HLA B27-associated diseases, and to examine potential animal models for these disease. Several of these diseases can result in arthropathies in humans, and lead to chronic disabling conditions. Present studies suggest that certain microbial ureases may act as a molecular mimic of HLA-B27, since the alpha subunit of ureases from Ureaplasma urealyticum, Klebsiella pneumoniae, Helicobacterpylori, Yersinia enterocolitica and Y, pseudotuberculosis cross-react with anti- B27 monoclonal antibody (MAb). Urease from U. urealythicum yields the strongest reaction. Native urease (Uu150K) from U. urealyticum will be purified, and a region of the urease alpha subunit (pep243) will be synthesized and purified. Both of these molecules will be tested as a molecular mimic of HLA-B27-transgenic mice (TGM). Certain strains of these mice have the potential to be animal model for studies of joint inflammation and arthritis characteristic B27-associated disease. To achieve the goals of this project, the specific aims are to 1) identify B27 expression in tissues from select strains of B27-TGM, using immunocytochemical analysis of histological sections; 2) identify cross reactivity between anti-pep243 MAb and HLA-B27 expressed on the cells of select strains of B27_ TGM; 3) examine cells, purified Uu150k, pep243, or H2B6 immunogen as test antigens; 4) examine B27 TGM and controls for the binding of newly synthesize antibody to specific tissues following inoculation with the test antigens; 5) assess binding inhibition of anti- pep243 MAb to specific tissues of B27+TGM following inoculation with the these antigens, to determine if the newly and control mice sera for anti- B27 anti-Uu150k, and anti-pep 243 antibodies, following inoculation with the test antigens. The data to be obtained will evaluate microbial urease as a mechanism of pathogenesis for B27 associated diseases, provide certain baseline immunocytochemical data for potential animal models to study these diseases, and test the efficacy of the potential animal models.